NAPAC2016 - List of Keywords (HOM)

Paper	Title	Other Keywords	Page
MOPOB16	Higher Order Modes Analysis of Fermilab's Recycler Cavity	impedance, cavity, ion, dipole	106
	M.H. Awida, J.E. Dey, T.N. Khabiboulline, V.A. Lebedev, R.L. Madrak Fermilab, Batavia, Illinois, USA
	Funding: Operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE Two recycler cavities are being employed in Fermilab's Recycler Ring for the purpose of slip stacking proton bunches, where 6 batches of 8 GeV protons coming from the Booster are stacked on top of 6 circulating batches. Slip stacking requires two RF cavities operating at 52.809 and 51.545 MHz. In this paper, we report on the analysis of higher order modes in the Recycler cavity, presenting the values for R/Q and shunt impedances. Knowing the frequencies and properties of higher order modes is particularly critical for beam physics and avoidance of beam instabilities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-MOPOB16
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MOPOB47	Beam Coupling Impedance Characterization of Third Harmonic Cavity for ALS Upgrade	ion, impedance, cavity, coupling	167
	T.H. Luo, K.M. Baptiste, M. Betz, J.M. Byrd, S. De Santis, S. Kwiatkowski, S. Persichelli, Y. Yang LBNL, Berkeley, California, USA
	The ALS upgrade to a diffraction-limited light source (ALS-U) depends on the ability to lengthen the stored bunches to limit the emittance growth and increase the beam life time. In order to achieve lengthening in excess of fourfold necessary to this end, we are investigating the use of the same passive 1.5 GHz normal-conducting RF cavities currently used on the ALS. While the upgraded ring RF parameters and fill pattern make it easier as long as the beam-induced phase transient is concerned, the large lengthening factor and the strongly non-linear lattice require particular attention to the cavities contribution to the machine overall impedance budget. In this paper we present our estimates of the narrow-band impedance obtained by numerical simulation and bench measurements of the cavities' resonant modes.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-MOPOB47
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MOPOB60	Performance of the Cornell Main Linac Prototype Cryomodule for the CBETA Project	cavity, ion, linac, cryomodule	204
	F. Furuta, N. Banerjee, J. Dobbins, R.G. Eichhorn, M. Ge, D. Gonnella, G.H. Hoffstaetter, M. Liepe, T.I. O'Connell, P. Quigley, D.M. Sabol, J. Sears, E.N. Smith, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	The main linac prototype cryomodule (MLC) is a key component for the Cornell-BNL ERL Test Accelerator (CBETA), which is a 4-turn FFAG ERL under construction at Cornell University. The MLC has been designed for high current and efficient continuous wave (CW) SRF cavity operation, and houses six high Q0 7-cell SRF cavities with individual beamline higher order-modes (HOMs) absorbers for strong HOM suppression in high beam current operation. Cavities have achieved specification values of 16.2MV/m with high Q0 of 2.0·10¹⁰ at 1.8K in CW operation after cooldown optimizations and RF processing. Damping of the HOMs has been measured in detail, indicating that the loaded quality-factors of all critical modes are low enough to avoid BBU in high current, multi-turn ERL operation. Microphonics measurements have been carried out as well, and vibration sources have been determined and eliminated. Here we report on these cryomodule performance studies.
	Poster MOPOB60 [3.321 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-MOPOB60
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WEB2IO02	Compact Crabbing Cavity Systems for Particle Colliders	cavity, ion, dipole, collider	679
	S.U. De Silva ODU, Norfolk, Virginia, USA
	In circular or ring-based particle colliders, crabbing cavities are used to increase the luminosity. The first superconducting crabbing cavity system was successfully implemented at KEKB electron-positron collider that have demonstrated the luminosity increase with overlapping bunches. Crabbing systems are an essential component in the future colliders with intense beams, such as the LHC high luminosity upgrade and proposed electron-ion colliders. Novel compact superconducting cavity designs with improved rf properties, at low operating frequencies have been prototyped successfully that can deliver high operating voltages. We present single cavity and multi-cell crabbing cavities proposed for future particle colliders and addresses the challenges in those cavity systems.
	Slides WEB2IO02 [13.985 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEB2IO02
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WEPOB27	Modification of 3rd Harmonic Cavity for CW Operation in LCLS-II Accelerator	ion, cavity, FEL, linac	960
	T.N. Khabiboulline, M.H. Awida, I.V. Gonin, A. Lunin, N. Solyak, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	A 3.9 GHz 3rd harmonic cavity was developed at FNAL and it is currently used in the FLASH accelerator at DESY in order to improve FEL operation. The European XFEL accelerator in Hamburg also adapted the same cavity design for a pulsed linac operation. The 3rd harmonic cavity for the LCLS-II accelerator at SLAC will operate in a continuous wave (CW) regime. A CW operation and a high average current in the LCLS-II linac result in in-creased heat loads to main and HOM couplers of the cavity. Several cavity design modifications were pro-posed and investigated for improving a cavity perfor-mance in the CW regime. In this paper we present results of the design review for proposed modifications
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOB27
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WEPOB62	Absolute Energy Measurement of the LEReC Electron Beam	ion, dipole, simulation, electron	1033
	S. Seletskiy, M. Blaskiewicz, A.V. Fedotov, D. Kayran, J. Kewisch, T.A. Miller, P. Thieberger BNL, Upton, Long Island, New York, USA
	The goal of future operation of the low energy RHIC Electron Cooling (LEReC) accelerator is to cool the RHIC ion beams. To provide successful cooling, the velocities of the RHIC ion beam and the LEReC electron beam must be matched with 10^-4 accuracy. While the energy of ions will be known with the required accuracy, the e-beam energy can have an initial offset as large as 5%. The final setting of the e-beam energy will be performed by observing either the Schottky spectrum of debunched ions co-traveling with the e-beam or the recombination signal. Yet, to start observing such signals one has to set the absolute energy of the electron beam with an accuracy better than 10^-2, preferably better than 5·10^-3. In this paper we discuss how such accuracy can be reached by utilizing the LEReC 180 degree bend as a spectrometer.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOB62
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THA2IO02	High Gradient PM Technology for Ultra-High Brightness Rings	ion, quadrupole, storage-ring, radiation	1077
	G. Le Bec, J. Chavanne ESRF, Grenoble, France
	Permanent magnets have long been major components in accelerator-based light sources, particularly as a part of insertion devices. However, their use as main lattice magnets (dipoles, quadrupoles) has been so far somewhat limited. The present trend towards small magnet apertures, exemplified by various multibend achromat designs currently under commissioning or design/construction opens up the discussion once more on the large-scale use of permanent magnets as a means to achieve extremely high gradients in future diffraction-limited storage rings. This paper will review the current R&D programs on the use of permanent magnets in the lattice of high brightness storage rings.
	Slides THA2IO02 [5.770 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-THA2IO02
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THPOA21	Multipacting in HOM Coupler of LCLS-II 1.3 GHz SC Cavity	ion, multipactoring, cavity, electron	1146
	G.V. Romanov, T.N. Khabiboulline, A. Lunin Fermilab, Batavia, Illinois, USA
	During high power tests of the 1.3 GHz LCLS-2 cavity on the test stand at Fermilab an anomalous rise of temperature of the pickup antenna in the higher order mode (HOM) coupler was detected in accelerating gradient range of 5-10 MV/m. It was suggested that the multipacting in the HOM coupler may be a cause of this temperature rise. In this work the suggestion was studied, and the conditions and the location, where multipacting can develop, were found.
	Poster THPOA21 [4.786 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-THPOA21
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THPOA31	Sector Magnets or Transverse Electromagnetic Fields in Cylindrical Coordinates	ion, multipole, dipole, electromagnetic-fields	1167
	T. Zolkin Fermilab, Batavia, Illinois, USA
	Laplace's equation in normalized cylindrical coordinates is considered for scalar and vector potentials describing electric or magnetic fields with invariance along the azimuthal coordinate (arXiv:1603.03451). A series of special functions are found which when expanded to lowest order in power series in radial and vertical coordinates (rho=1 and y=0) replicate harmonic homogeneous polynomials in two variables. These functions are based on radial harmonics found by Edwin M. McMillan forty years ago. In addition to McMillan's harmonics, a second family of radial harmonics is introduced to provide a symmetric description between electric and magnetic fields and to describe fields and potentials in terms of the same functions. Formulas are provided which relate any transverse fields specified by the coefficients in the power series expansion in radial or vertical planes in cylindrical coordinates with the set of new functions. This result is important for potential theory and for theoretical study, design and proper modeling of sector dipoles, combined function dipoles and any general sector element for accelerator physics and spectrometry.
	Poster THPOA31 [2.274 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-THPOA31
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Other Keywords

Page

MOPOB16

Higher Order Modes Analysis of Fermilab's Recycler Cavity

impedance, cavity, ion, dipole

106

M.H. Awida, J.E. Dey, T.N. Khabiboulline, V.A. Lebedev, R.L. Madrak
Fermilab, Batavia, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE
Two recycler cavities are being employed in Fermilab's Recycler Ring for the purpose of slip stacking proton bunches, where 6 batches of 8 GeV protons coming from the Booster are stacked on top of 6 circulating batches. Slip stacking requires two RF cavities operating at 52.809 and 51.545 MHz. In this paper, we report on the analysis of higher order modes in the Recycler cavity, presenting the values for R/Q and shunt impedances. Knowing the frequencies and properties of higher order modes is particularly critical for beam physics and avoidance of beam instabilities.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-MOPOB16

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPOB47

Beam Coupling Impedance Characterization of Third Harmonic Cavity for ALS Upgrade

ion, impedance, cavity, coupling

167

T.H. Luo, K.M. Baptiste, M. Betz, J.M. Byrd, S. De Santis, S. Kwiatkowski, S. Persichelli, Y. Yang
LBNL, Berkeley, California, USA

The ALS upgrade to a diffraction-limited light source (ALS-U) depends on the ability to lengthen the stored bunches to limit the emittance growth and increase the beam life time. In order to achieve lengthening in excess of fourfold necessary to this end, we are investigating the use of the same passive 1.5 GHz normal-conducting RF cavities currently used on the ALS. While the upgraded ring RF parameters and fill pattern make it easier as long as the beam-induced phase transient is concerned, the large lengthening factor and the strongly non-linear lattice require particular attention to the cavities contribution to the machine overall impedance budget. In this paper we present our estimates of the narrow-band impedance obtained by numerical simulation and bench measurements of the cavities' resonant modes.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-MOPOB47

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPOB60

Performance of the Cornell Main Linac Prototype Cryomodule for the CBETA Project

cavity, ion, linac, cryomodule

204

F. Furuta, N. Banerjee, J. Dobbins, R.G. Eichhorn, M. Ge, D. Gonnella, G.H. Hoffstaetter, M. Liepe, T.I. O'Connell, P. Quigley, D.M. Sabol, J. Sears, E.N. Smith, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

The main linac prototype cryomodule (MLC) is a key component for the Cornell-BNL ERL Test Accelerator (CBETA), which is a 4-turn FFAG ERL under construction at Cornell University. The MLC has been designed for high current and efficient continuous wave (CW) SRF cavity operation, and houses six high Q0 7-cell SRF cavities with individual beamline higher order-modes (HOMs) absorbers for strong HOM suppression in high beam current operation. Cavities have achieved specification values of 16.2MV/m with high Q0 of 2.0·10¹⁰ at 1.8K in CW operation after cooldown optimizations and RF processing. Damping of the HOMs has been measured in detail, indicating that the loaded quality-factors of all critical modes are low enough to avoid BBU in high current, multi-turn ERL operation. Microphonics measurements have been carried out as well, and vibration sources have been determined and eliminated. Here we report on these cryomodule performance studies.

Poster MOPOB60 [3.321 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-MOPOB60

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEB2IO02

Compact Crabbing Cavity Systems for Particle Colliders

cavity, ion, dipole, collider

679

S.U. De Silva
ODU, Norfolk, Virginia, USA

In circular or ring-based particle colliders, crabbing cavities are used to increase the luminosity. The first superconducting crabbing cavity system was successfully implemented at KEKB electron-positron collider that have demonstrated the luminosity increase with overlapping bunches. Crabbing systems are an essential component in the future colliders with intense beams, such as the LHC high luminosity upgrade and proposed electron-ion colliders. Novel compact superconducting cavity designs with improved rf properties, at low operating frequencies have been prototyped successfully that can deliver high operating voltages. We present single cavity and multi-cell crabbing cavities proposed for future particle colliders and addresses the challenges in those cavity systems.

Slides WEB2IO02 [13.985 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEB2IO02

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPOB27

Modification of 3rd Harmonic Cavity for CW Operation in LCLS-II Accelerator

ion, cavity, FEL, linac

960

T.N. Khabiboulline, M.H. Awida, I.V. Gonin, A. Lunin, N. Solyak, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

A 3.9 GHz 3rd harmonic cavity was developed at FNAL and it is currently used in the FLASH accelerator at DESY in order to improve FEL operation. The European XFEL accelerator in Hamburg also adapted the same cavity design for a pulsed linac operation. The 3rd harmonic cavity for the LCLS-II accelerator at SLAC will operate in a continuous wave (CW) regime. A CW operation and a high average current in the LCLS-II linac result in in-creased heat loads to main and HOM couplers of the cavity. Several cavity design modifications were pro-posed and investigated for improving a cavity perfor-mance in the CW regime. In this paper we present results of the design review for proposed modifications

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOB27

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPOB62

Absolute Energy Measurement of the LEReC Electron Beam

ion, dipole, simulation, electron

1033

S. Seletskiy, M. Blaskiewicz, A.V. Fedotov, D. Kayran, J. Kewisch, T.A. Miller, P. Thieberger
BNL, Upton, Long Island, New York, USA

The goal of future operation of the low energy RHIC Electron Cooling (LEReC) accelerator is to cool the RHIC ion beams. To provide successful cooling, the velocities of the RHIC ion beam and the LEReC electron beam must be matched with 10^-4 accuracy. While the energy of ions will be known with the required accuracy, the e-beam energy can have an initial offset as large as 5%. The final setting of the e-beam energy will be performed by observing either the Schottky spectrum of debunched ions co-traveling with the e-beam or the recombination signal. Yet, to start observing such signals one has to set the absolute energy of the electron beam with an accuracy better than 10^-2, preferably better than 5·10^-3. In this paper we discuss how such accuracy can be reached by utilizing the LEReC 180 degree bend as a spectrometer.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOB62

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THA2IO02

High Gradient PM Technology for Ultra-High Brightness Rings

ion, quadrupole, storage-ring, radiation

1077

G. Le Bec, J. Chavanne
ESRF, Grenoble, France

Permanent magnets have long been major components in accelerator-based light sources, particularly as a part of insertion devices. However, their use as main lattice magnets (dipoles, quadrupoles) has been so far somewhat limited. The present trend towards small magnet apertures, exemplified by various multibend achromat designs currently under commissioning or design/construction opens up the discussion once more on the large-scale use of permanent magnets as a means to achieve extremely high gradients in future diffraction-limited storage rings. This paper will review the current R&D programs on the use of permanent magnets in the lattice of high brightness storage rings.

Slides THA2IO02 [5.770 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-THA2IO02

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPOA21

Multipacting in HOM Coupler of LCLS-II 1.3 GHz SC Cavity

ion, multipactoring, cavity, electron

1146

G.V. Romanov, T.N. Khabiboulline, A. Lunin
Fermilab, Batavia, Illinois, USA

During high power tests of the 1.3 GHz LCLS-2 cavity on the test stand at Fermilab an anomalous rise of temperature of the pickup antenna in the higher order mode (HOM) coupler was detected in accelerating gradient range of 5-10 MV/m. It was suggested that the multipacting in the HOM coupler may be a cause of this temperature rise. In this work the suggestion was studied, and the conditions and the location, where multipacting can develop, were found.

Poster THPOA21 [4.786 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-THPOA21

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPOA31

Sector Magnets or Transverse Electromagnetic Fields in Cylindrical Coordinates

ion, multipole, dipole, electromagnetic-fields

1167

T. Zolkin
Fermilab, Batavia, Illinois, USA

Laplace's equation in normalized cylindrical coordinates is considered for scalar and vector potentials describing electric or magnetic fields with invariance along the azimuthal coordinate (arXiv:1603.03451). A series of special functions are found which when expanded to lowest order in power series in radial and vertical coordinates (rho=1 and y=0) replicate harmonic homogeneous polynomials in two variables. These functions are based on radial harmonics found by Edwin M. McMillan forty years ago. In addition to McMillan's harmonics, a second family of radial harmonics is introduced to provide a symmetric description between electric and magnetic fields and to describe fields and potentials in terms of the same functions. Formulas are provided which relate any transverse fields specified by the coefficients in the power series expansion in radial or vertical planes in cylindrical coordinates with the set of new functions. This result is important for potential theory and for theoretical study, design and proper modeling of sector dipoles, combined function dipoles and any general sector element for accelerator physics and spectrometry.

Poster THPOA31 [2.274 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-THPOA31

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)